Using Android in Education for Mobile Device DevelopmentDocument Transcript
Using Android in Education for Mobile Device
Chris Baker and Danny Noler
July 2, 2008
In the growing world of technology, cellular devices have quickly
emerged as one of the fastest evolving ﬁelds. They have increased
greatly in both popularity and complexity, requiring more advanced
operating systems and applications to meet the demands of the con-
sumer. Android is a software stack designed to meet these demands in
an open source environment. The project is currently being developed
and funded by the Open Handset Alliance, which includes companies
such as Google and T-Mobile. Android includes an operating system,
middleware, and key applications, as well as a Software Development
Kit (SDK) for developers to create their own applications for the An-
droid environment. Due to its open source license and tools provided,
Android is an ideal platform for bringing the mobile market to the
This paper describes in detail what Android is, its architecture,
and why developers should choose Android to develop in a mobile de-
vice platform environment. The paper also discusses the basic hard-
ware requirements for porting the current version of Android to real
hardware. Finally, it discusses some of the obstacles we are faced with,
our achievements with porting Android to a Nokia N800 and a Sharp
Zaurus SL-C3200, and the lessons we learned during this process.
1 What is Android?
Android is a software stack currently being developed by Google for mobile
devices. In 2007 the Open Handset Alliance was formed, which consists of
more than 30 technology and mobile companies such as Intel, HTC, Mo-
torola, etc. This alliance is headed by Google, with each company helping
to develop open standards for mobile devices. Android is the ﬁrst complete
and open mobile platform using this new standard. Android uses a Linux
kernel (version 2.6) to achieve many core system services such as memory
management, security, and even a network stack to provide a secure and sta-
ble environment for its architecture. The overlying software consists of three
parts that work together to form a working software stack for mobile devices.
Android includes its own userspace on top of the Linux kernel, which contains
the APIs necessary for Android applications. It is also responsible coordi-
nating activities that take place within the computer. Above the operating
system lies middleware components. This is the software that connects soft-
ware components or other applications to each other. Middleware is used to
distribute services across multiple processes running on the computer. Key
applications combine to form the ﬁnal part of Android. This includes the
basic applications found on most smart phones that are on the market today.
A browser, contact list, map application, and the phone software itself are
all key applications that are found within the Android architecture.
2 Why Choose Android?
In order to attract developers, Google promotes four main features of An-
droid. The ﬁrst is its open nature. This means that Android’s API will be
freely available to any programmer who wishes to create an Android applica-
tion. The second feature is the application hierarchy. All applications are on
an equal playing ﬁeld, meaning even a phone’s basic applications (such as the
dialer) can be replaced by third party programs. Android also combines in-
formation from the web with data on the phone. For example, one could use
contact information stored on the phone to determine the geographic loca-
tion of the contact’s home using information stored online. Finally, Android
includes a Software Development Kit in order to expediate application design
and implementation. The SDK includes everything a developer needs to be-
gin writing Android applications, which are written in the Java programming
3 Hardware Requirements for Android
Although the source code for Android has not been oﬃcially released, it is
still possible to port Android to real hardware. By using a compiled Linux
kernel and applying the necessary Android patches, one can port Android
to a real device and run a version of Android on the device. Android is
currently very hardware speciﬁc and when choosing a device to port to, one
must abide by the minimum hardware requirements. Since Google has not
released the source code to Android, only code available in the SDK can
be used. The SDK itself uses an open source processor emulator, known as
QEMU, to create a virtual ARM system-on-a-chip (SoC) known as Goldﬁsh.
The ARM SoC boots a 2.6.23 ARM Linux kernel with support for the Gold-
ﬁsh platform on a x86 host. Since Goldﬁsh contains software compiled for
the ARMv5 instruction set, only hardware with an ARM926 or higher can
be used. Suﬃcient main memory is 32MB, but this is only enough to run
Android at a very basic level and should only be used as a proof of concept.
A higher amount of main memory should be used in order to obtain a us-
able system. These are the minimum hardware prerequisites that must be
met in order to port and run Android on real hardware. There have been
many documented successful attempts at porting Android to real hardware.
This paper also shares some of our successes and achievements with porting
Android to a device. 
4 Educational Use
A great deal of work has been done with Android, but one might wonder
what purpose work like ours serves. Our ultimate goal to show that Android
is an excellent tool for learning. Given its open source nature, there is a great
deal of resources available for both programmers and hackers. Google has
already released a full SDK for Android, allowing developers to write applica-
tions and test them using an emulator, although applications can be ported
to devices on which Android has been hacked and test them there. There is
also a thriving community of enthusiasts who provide insights into Android’s
mechanics and their experiences with porting the software. This provides an
ideal environment for educating others on mobile device development, which
has a diﬀerent philosophy from desktop development (emphasis on eﬃciency
and use of memory is critical in order to save battery and prevent system
lockup, for example). Also, hacking Android onto diﬀerent mobile devices
provides some insight into cross-compiling and device driver programming.
Given the current trend of continually shrinking computers and electronic
devices, it is vital that the next generation of computer scientists and engi-
neers have a grasp on mobile development. Android gives these students an
opportunity to see the front lines of development. Once Android is ﬁnally
completed and released on actual devices, its community is destined to grow
further, and application development will become more widespread. In turn,
more resources will become available, and students will ﬁnd an information
gold mine on the subject. Also, the release of the source code will allow up-
coming engineers and computer scientists to see the physical code that goes
into a mobile platform.
There are a number of obstacles that must be overcome in order to work with
Android. The greatest and most obvious is the learning curve. Those familiar
with Linux kernels, device driver programming, and cross compilers will no
doubt have an advantage while porting Android. Also, the architecture must
be understood before programming any application to run on an Android
device. Both of these presented an initial (and continuing) challenge to us,
as neither of us have ever worked this deeply with Linux. This is also our
ﬁrst work with Android. However, these issues can be overcome through
literature and other sources of information. Google provides an impressive
guide for Android and application programming. Message boards are also
available for communication with other developers. Linux development also
has a wide selection of resources both online and in print. It is up to each
individual to determine which sources best meet their needs.
There is one other large obstacle, though not permanent. Since Google
has not released an oﬃcial Android device for purchase, they have not re-
leased the full source code to Android. This is the reason why an ARM
architecture is required for porting Android, as the source has not been com-
piled for x86 processors. Therefore, Android must be ”patched” together
using a combination of a Linux kernel, Android patches speciﬁc to a particu-
lar board, and any other patches needed for hardware ﬁxes such as keyboard
and touchscreen functionality. While this does allow for an added diﬃculty
that some might ﬁnd exciting and challenging, it also prevents Android from
being used on machines that would otherwise meet basic Android require-
ments. The ﬁrst Android device is expected in Q4 2008 or Q1 2009, at which
point the source code for Android will be released to the public. At this
time, this obstacle can only be overcome through ingenuity and through the
successes of others who post their stories online.
6 Achievements and Lessons Learned
6.1 Android on Nokia N800
The ﬁrst real hardware device that we began work with was the Nokia N800
internet tablet. This device has WiFi and touchscreen capabilities which
Android supports. One of the ﬁrst steps we took with the N800 was to up-
date the native operating system to OS2008. Before beginning the process
of porting Android to the N800, we downloaded and installed the necessary
tools and ﬁles that would be needed to achieve a successful port of the An-
droid image. These ﬁles included the 2.6.21 Linux kernel, an ARM GNU
Toolchain for cross- compiling, Maemo ﬂasher 3.0, prebuilt Android ﬁle sys-
tem, touchscreen patch speciﬁc to the N800, and an Android patch which
was derived from the SDK and is speciﬁc for the N800 (version 1). There are
newer versions of this patch (versions 2 and 3) available, but these patches
were designed speciﬁcally for the N810 and will not be fully compatible for
the N800. A microSD card was formatted using the ext2 standard and the
system ﬁles were then copied to the card.
We began the actual process of porting Android to the N800 by applying
the necessary patches to the Linux kernel source. First we patched the ker-
nel source with the Android version 1 patch followed by applying the N800
touchscreen patch to the source. After the patches were applied, we cross-
compiled the source using the ARM GNU Toolchain in order to obtain a
version that was compatible with an ARM architecture. An Android im-
age ﬁle is produced by this cross- compilation. The Maemo ﬂasher 3.0 tool
was then used to ﬂash the image to the N800 device. Once the image was
successfully ﬂashed to the N800, we took the microSD card containing the
Android ﬁle system and placed it in the N800. By using a custom startup
Figure 1: Chris holding the N800 with Android running
script designed to mount the ﬁle system on the N800, we were then able
to successfully start Android and obtain a working Android device. Please
note the native OS2008 is not overwritten, and is still the default system
booted when the N800 is turned on. The startup script must be run from
the Terminal once inside OS2008.
It should be mentioned that we used the m3 release of Android for the
user space while using the m5 release to patch the Linux kernel. This is done
because the Linux kernel will not support some of the newer features on the
m5 system, such as double buﬀer support in the frame buﬀer driver. Also,
the N800 lacks both a physical and virtual keyboard. Therefore, it is not
possible to test text input with the web browser once inside of Android.
6.2 Android on Sharp Zaurus SL-C3200
Our ﬁnal device was the Zaurus SL-C3200. This device has several and-
vantages over the Nokia N800, including a full QWERTY keyboard, a six
gigabyte hard drive, and a faster processor. However, it proved to be more
challenging than the N800. Initially, we just wanted to check Android’s us-
ability on the device. We found an Android enthusiast who had uploaded
pre-compiled images of the Linux kernel and Android m3 userspace for the
C3200. We downloaded the ﬁles, copied them to an SD card, and updated
the Zaurus using its built in update tool. All went well, and within ten min-
utes we had a working Android device. Unfortunately, the touch screen was
not functional, and without a built-in WiFi card, we also could not access
the Internet. However, all the applications were functional.
From there, we decided to attempt to compile our own linux kernel. With
this method, we could apply touch screen patches and try the m5 userspace,
which some developers had gotten to work on the C3200. Before we started
with the Zaurus, we ﬁrst had to download and install OpenEmbedded, an
open source cross-compiler. This was a hastle in itself, as there was not much
documentation on conﬁguring and building the tool chain. After several days
of trail and error, we were ﬁnally able to build the tool using instructions
spliced from several websites.[3, 6]
After building the tool, we compiled a linux kernel image for the C3200
architecture. This particular image is known as the Angstrom Distribution,
and was created speciﬁcally for embedded devices. We altered some conﬁg-
uration ﬁles in order to apply the necessary Android patches to the kernel.
The complilation itself took almost half a day. From there, we copied the
Linux ﬁles over to an SD card and updated the Zaurus in the same fashion
as before. Once the system was successfully formated, we had a working
Linux distribution, though there was no GUI as of yet. From here, we ex-
tracted the Android ﬁle system. Luckily, Google provides these ﬁles as an
image ﬁle in their SDK. We extracted the image on the Zaurus, created a
small startup script, and ﬁred up Android. Unfortunately, Android would
not load past its moving red cylon bar. After doing some research online, we
discovered we were missing a kernel module called Binder. We managed to
ﬁnd Binder online, and attempted to insert it into the kernel. However, the
Binder module was created for Linux kernel version 2.6.23, and 2.6.26 was
installed on the Zaurus. At this point we were near the end of our summer
session, and unfortunately could not determine how to build an Angstrom
Figure 2: Danny holding the C3200 with Android running
Distribution with kernel version 2.6.23. However, this project is not without
its successes. We learned a great deal about cross compilers, linux make ﬁles,
and scripts.[3, 8]
Android has come a long way since its inception three years ago. It will
surely impact the mobile market when the ﬁrst Android phones are released,
but also provides an excellent opportunity for developers to enter the mobile
market. A great deal can be learned by both creating applications using
Android’s unique Java API as well as attempting to port Android to real
hardware. The classroom can beniﬁt from Android, given the amount of
resources available for reference. Given the market trend towards the mobile
market, future developers can greatly beniﬁt by using Android to improve
their algorithms and resource management. Since it is open source, there is
no cost to learn. Android is a win-win situation for both the community and
 Alextreme. Android on n810 - binaries and a ﬁxed tutorial. http://www.
alextreme.org/drupal/?q=android_on_n810, May 2008. Blog entry
where m3 Android userspace was downloaded.
 Cortez. Android on zaurus. http://www.omegamoon.com/blog/static.
php?page=ZaurusAndroid, July 2008. Blog entry where m3 Android ﬁles
were downloaded for Zaurus.
 Andy Dinosaur. Google android runs on sharp zaurus sl-c3000. http://
androidzaurus.seesaa.net/article/74237419.html, December 2007.
Blog entry specifying how to use OpenEmbedded to put Android on Za-
 User generated Wiki. Android on nokia n8xx. http://code.google.
com/p/android-on-n8xx/wiki/Home, June 2008.
 User generated Wiki. Android on omap. http://elinux.org/Android_
 User generted Wiki. Getting started. http://wiki.openembedded.net/
index.php/Getting_Started, June 2008. How to install OpenEmbed-
ded tool chain and compile images.
 Google. Android home page. http://code.google.com/android, 2008.
 lardman. Spitz installation instructions. http://www.
2007. How to install Angstrom on Spitz (SL-C3200 hardware).
 NuuNeol. http://groups.google.com/group/android-internals/
2008. Message board post where Nokia N800 touchscreen patch was